Method and Device For Producing Technical Glass Parts For Optical Applications

ABSTRACT

The present invention relates to a method for producing a technical glass part, particularly meeting high requirements with respect to contour accuracy and surface quality, particularly a precision lens, wherein a blank including a cast-on section is produced using an injection molding process, wherein the blank is cooled down and subsequently heated, and wherein the blank subsequently is blank molded, particularly on both sides, into a technical glass part meeting high requirements with respect to contour accuracy and surface quality, particularly a precision lens.

FIELD OF THE INVENTION

The present invention relates to a device and a method for producing atechnical glass part, particularly meeting high requirements withrespect to contour accuracy and/or surface quality. Such a technicalglass part may be an optical lens, particularly a precision lens, anoptical freeform or a technical glass article meeting high requirementswith respect to contour accuracy and surface quality. A technical glasspart is meant to be a technical glass part for optical applications.

BACKGROUND

Devices and methods for producing precision lenses are known, forexample, from US 2006/0107697 A1, EP 0356 068 B1, EP 1 273 424 A1, DE198 26 385 A1 as well as Patent Abstracts of Japan to JP 63182223 A, JP62292636 A, JP 62292630 A, JP 62292629 A, JP 61266320 A, JP 61242921 A,JP 61242920 A, JP 57041155 A, JP 58177257 A, JP 11333686, JP 09277327 A,JP 60033221 A and JP 01298034 A.

DE 103 23 989 B4 discloses a device for implementing a method forproducing blank molded glass bodies for optical equipments, wherein aliquid glass gob is supplied to a levitation pre-mould in which theglass gob without contacting the pre-mould is blanked into a blank whichafter elapse of a predefined time is transferred to a separate pressmould and pressed therein using a molding tool into an end form, whereinthe transfer of the blank to the press mould is conducted in such a waythat the blank is falling in a free fall from the pre-mould into thepress mould, wherein the pre-mould for transferring the glass gob isshifted over the press mould, is stopped in this transfer position andis pivoted away downwardly from the glass gob using two turntables, oneof which includes circularly disposed pre-moulds for forming said blanksfrom a liquid glass gob which include in the lower portion thereof minorholes for building in an air cushion and the other includes circularlydisposed press moulds for molding the blanks after transfer out of thepre-moulds, and wherein each pre-mould is attached to the firstturntable via a switchable holder holding the pre-mould in a firstswitching position horizontally and in a second switching positionholding the pre-mould in a position enabling the free fall of theblanks.

DE 101 40 626 B4 discloses a method for producing a press formed glassbody, wherein a molten glass mass is poured into a mould, pressed withinthe mould using a press ram and cooled down and subsequently removedfrom the mould as the press formed glass body, wherein the molten glassmass in the mould is subjected several molding processes, whereinbetween the molding processes a cooling process occurs and at least oncebetween the molding processes a heating process for heating the outerregions of the glass mass is conducted such that the cooling of theglass mass in the outer region is matched to the cooling within thecore.

DE 102 34 234 A1 discloses a method of blank molding a glass body foroptical applications using a press mould including an upper mould and alower mould and optionally a ring for receiving the glass body heated toa temperature above its deformation temperature, wherein an electricalvoltage is applied between the upper mould and the lower mould and atleast after matching the temperature of the glass body to thetemperature of the press mould a compression pressure is applied to theglass body.

DE 103 48 947 A1 discloses a press for hot forming optical elements madeof glass including a device for heating a mould block including an uppermould, a lower mould and a guiding ring for receiving the glassmaterial, wherein as a heating mechanism an inductive heating isprovided and the mould block is disposed on top of a thermicallyisolating body during the heating process.

DE 196 33 164 C2 discloses a method and a device for blank moldingoptical components for illuminating purposes at least on one side,wherein at least one mechanically portioned glass part is transferred bya gripper to at least one annular receptacle extendable from at leastone oven and moved from the receptacle into the oven and is heatedtherein on the receptacle, wherein the heated glass part is moved fromthe receptacle out of the oven and is again transferred to the gripperwhich supplies the heated glass part to a press for blank molding theglass part at least on one side, and wherein the blank molded glass partis then removed from the press, transferred to a cooling zone andcarried away from there.

DE 103 60 259 A1 discloses a method of blank molding optical elementsmade of glass, wherein a glass gob arranged in a mould block is heatedto a temperature T above its transformation temperature T_(G), the glassgob is pressed and cooled down to a temperature lower than T_(G),wherein the cooling process initially is conducted in a firsttemperature interval above T_(G) using a first cooling rate and then ina second temperature interval including T_(G) using a second coolingrate, and wherein for adjusting the first and second cooling rate anactive cooling is conducted.

DE 44 22 053 C2 discloses a method of producing glass forms, wherein ina pressing station molten glass is pressed in a press mouldpredetermining the exterior shape of the glass form using a press rampredetermining its interior shape, wherein the press ram remains incontact with the glass form within the press mould and thus dissipatesheat from the surface of the glass form only for a time until the glassform has cooled down in a near-surface area to such a temperature thatit includes an inherent rigidity sufficient for removing the glass formfrom the press mould, and wherein the glass form subsequently is removedfrom the press mould and transferred to a cooling station before itbecomes deformed due to partially heating and the glass form is cooleddown in the cooling station until it is completely solidified.

Other methods and devices for producing optical components are disclosedfor example in JP 09132417 A, JP 10251030 A, EP 1 584 863 A2 and EP 0078 658 B2.

It is an object of the invention to decrease the costs for producingtechnical glass parts meeting high requirements with respect to contouraccuracy and/or surface quality, particularly precision lenses, comparedto known methods.

SUMMARY

The above object is achieved by a method for producing a technical glasspart, particularly meeting high requirements with respect to contouraccuracy and/or surface quality, particularly a precision lens, whereina blank is produced using an injection molding process, wherein theblank is cooled and subsequently heated, and wherein the blanksubsequently is blank molded, particularly on both sides, into atechnical glass part, particularly meeting high requirements withrespect to contour accuracy and/or surface quality, particularly aprecision lens.

Appropriate glass types are for example B270, F2, DOCTAN® andborosilicate glass. A precision lens in the sense of the inventionparticularly is a lens the contour of which deviates from a desiredtarget contour by not more than 2 μm, particularly not more than 1 μm,and/or the surface roughness of which is not more than 5 nm.Particularly, surface roughness in the sense of the invention should bedefined according to ISO 4287 as R_(a). Blank molding in the sense ofthe invention particularly means molding a glass part or a precisionlens such that a post-treatment of an optically effective surface of aglass part or the precision lens, particularly a post-treatment forachieving its desired contour, after the molding process, may beomitted.

Examples for injection molding of glass parts can be found on Internetsite www.putsch.com/Pu_Ge_Su/deutsche Version/Ebene5/FraSets/FSGlas/FSSIM.html. Injection presses for glass parts are available from PutschGmbH & Co. KG, Frankfurter Straβe 5-21, 58095 Hagen, Deutschland.

In a further embodiment of the invention the blank is produced includinga cast-on section by using an injection molding process, wherein thevolume of the cast-on section may be larger than the volume of theblank. In a further embodiment of the invention the volume of thecast-on section is more than twice the volume of the blank. In a furtherembodiment of the invention the cast-on section includes a bulge. In afurther embodiment of the invention the blank is held suspended duringthe cooling process and/or during the heating process.

In a further embodiment of the invention the cast-on section includes asupporting foot, and in a further embodiment of the invention it isconsidered that the blank is mounted upright by provision of thesupporting foot during the cooling and/or heating process.

In a further embodiment of the invention the cast-on section isconstructed at least in two pieces. A cast-on section in this sense isconstructed at least in two pieces if it includes at least two partswhich are not connected directly but via the blank.

In a further embodiment of the invention the cast-on section includes atleast a cylindrically formed part. In a further embodiment of theinvention a spherical diameter associated to the blank, a sphericaldiameter of the blank and/or the diameter of the blank is at least twicethe diameter of the cylindrically formed part. In a further embodimentof the invention the length of the cylindrically formed part is at leasttwice the diameter of the cylindrically formed part.

In a further embodiment of the invention the blank is cooled down withsupply of heat. In a further embodiment of the invention the blank iscooled down at a temperature between 300° C. and 500° C., particularlybetween 350° C. and 450° C. In a further embodiment of the invention theblank is cooled down at a temperature between 20K and 200K, particularlybetween 70K and 150K, beneath the transformation temperature T_(G) ofthe glass of the blank.

In a further embodiment of the invention the blank is cooled down andsubsequently heated such that its temperature gradient is inverted orreversed. In a further embodiment of the invention the blank is heatedsuch that its surface temperature (particularly immediately before themolding process) is in the range between 700° C. and 900° C.,particularly between 750° C. and 850° C. In a further embodiment of theinvention the blank is heated such that its surface (particularlyimmediately before the molding process) assumes a temperaturecorresponding to a temperature at which the glass of the blank has alogarithmic viscosity or viscosity-log value between 5 (corresponding to10⁵ Pas) and 8 (corresponding to 10⁸ Pas), particularly a viscosity-logvalue between 5.5 (corresponding to 10^(5.5) Pas) and 7 (correspondingto 10⁷ Pas). The temperature gradient may be adjusted such that thetemperature within the core of the blank is lower than or close to thetransformation temperature T_(G) of the glass. The transformationtemperature T_(G) of the glass is the temperature at which the glassbecomes hardened. The transformation temperature T_(G) of the glass inthe sense of the invention should mean a temperature of the glass atwhich the glass has a viscosity-log value in a range around 13.2(corresponding to 10^(13.2) Pas), particularly between 13 (correspondingto 10¹³ Pas) and 14.5 (corresponding to 10^(14.5) Pas)

In a further embodiment of the invention the blank is not touched duringthe cooling and/or heating process. In a further embodiment of theinvention the blank is not touched at a surface provided as an opticallyeffective surface during the cooling and/or heating process. In afurther embodiment of the invention the blank is not touched at asurface provided as an optically effective surface except during themolding process. In a further embodiment of the invention the blank isnot touched at a surface provided as an optically effective surfacebefore conducting the molding process. In a further embodiment of theinvention the blank is not touched at a surface provided as an opticallyeffective surface between the injection molding process and the moldingprocess.

In a further embodiment of the invention the blank via a horizontalpress is blank molded into the technical glass part, particularlymeeting high requirements with respect to contour accuracy and/orsurface quality, particularly a precision lens. In a further embodimentof the invention the cast-on section is removed after molding thetechnical glass part, particularly meeting high requirements withrespect to contour accuracy and/or surface quality, particularly aprecision lens.

In a further embodiment of the invention the technical glass part,particularly meeting high requirements with respect to contour accuracyand/or surface quality, particularly a precision lens, is cooled downafter the molding process with supply of heat, wherein it may beconsidered that the cast-on section is removed after cooling down thetechnical glass part, particularly meeting high requirements withrespect to contour accuracy and/or surface quality, particularly aprecision lens. Herein according to a further embodiment of theinvention the technical glass part, particularly meeting highrequirements with respect to contour accuracy and/or surface quality,particularly a precision lens, is mounted suspended or supported uprightby provision of a supporting foot during the cooling process.

In a further embodiment of the invention the volume of the blank amountsto between 110% and 130% of the volume of the technical glass part,particularly meeting high requirements with respect to contour accuracyand/or surface quality, particularly a precision lens.

The above object is also achieved by a method of producing a technicalglass part, particularly meeting high requirements with respect tocontour accuracy and/or surface quality, particularly a precision lens,wherein a blank is produced, and wherein the blank is cooled down andsubsequently heated such that its temperature gradient is inverted, andwherein the blank subsequently is blank molded, particularly on bothsides, into a technical glass part, particularly meeting highrequirements with respect to contour accuracy and/or surface quality,particularly a precision lens.

Appropriate glass types are for example B270, F2, DOCTAN® andborosilicate glass. In a further embodiment of the invention the blankis cooled down with supply of heat. In a further embodiment of theinvention the blank is cooled down at a temperature between 300° C. and500° C., particularly between 350° C. and 450° C. In a furtherembodiment of the invention the blank is cooled down at a temperaturebetween 20K and 200K, particularly between 70K and 150K, beneath thetransformation temperature T_(G) of the glass of the blank. In a furtherembodiment of the invention the blank is heated such that its surfacetemperature is in the range between 700° C. and 900° C., particularlybetween 750° C. and 850° C. In a further embodiment of the invention theblank is heated such that its surface assumes a temperaturecorresponding to a temperature at which the glass of the blank has aviscosity-log value between 5 (corresponding to 10⁵ Pas) and 8(corresponding to 10⁸ Pas), particularly a viscosity-log value between5.5 (corresponding to 10^(5.5) Pas) and 7 (corresponding to 10⁷ Pas).

In a further embodiment of the invention the blank is not touched duringthe cooling and/or heating process. In a further embodiment of theinvention the blank is not touched at a surface provided as an opticallyeffective surface during the cooling and/or heating process. In afurther embodiment of the invention the blank is not touched at asurface provided as an optically effective surface except during themolding process. In a further embodiment of the invention the blank isnot touched at a surface provided as an optically effective surfacebefore conducting the molding process. In a further embodiment of theinvention the blank is not touched at a surface provided as an opticallyeffective surface between the injection molding process and the moldingprocess.

In a further embodiment of the invention the blank by provision of ahorizontal press is blank molded into the technical glass part,particularly meeting high requirements with respect to contour accuracyand/or surface quality, particularly a precision lens.

The above object is also achieved by a device for producing a technicalglass part, particularly meeting high requirements with respect tocontour accuracy and/or surface quality, particularly a precision lens,particularly for carrying out a method including one or more of theabove mentioned features, wherein the device includes a meltingaggregate, an injection press for molding a blank, a tempering devicefor cooling down and subsequently heating said blank and a press formolding from said blank a technical glass part, particularly meetinghigh requirements with respect to contour accuracy and/or surfacequality, particularly a precision lens.

In an embodiment of the invention the injection press includes a pressmould for molding the blank with a cast-on section. In a furtherembodiment of the invention the press is constructed as a horizontalpress.

Cooling down with supply of heat in the sense of the inventionparticularly should mean that the cooling process is conducted at atemperature above 100° C.

It is particularly considered that the blank before inverting thetemperature gradient is removed from the injection press or acorresponding injection press mould or a mould. It is particularlyconsidered that inverting the temperature gradient takes place outsidean injection press mould or a mould.

Example embodiments of the invention also relate to a device and amethod for producing a headlight lens for a motor vehicle headlight.FIG. 9 shows a general arrangement drawing of a typical motor vehicleheadlight 201 including a light source 210 for generating light, areflector 212 for reflecting light producible via the light source 210and an aperture 214. The motor vehicle headlight 201 also includes aheadlight lens 202 for changing the radiation direction of lightproducible by the light source 210 and for imaging an edge 215 of theaperture 214 as a brightness-darkness boundary 220. The headlight lens202 includes a lens body 203, particularly made of glass, including anessentially planar surface 205 facing to the light source 210 and anessentially convex surface 204 facing away from the light source 210.The headlight lens 202 also includes an (optional) edge 206 via whichthe headlight lens 202 can be fixed within the vehicle headlight 201.

Methods of producing headlight lenses for motor vehicles are disclosed,for example, in DE 103 23 989 B4, DE 196 33 164 C2, DE 10 2004 018 424A1, DE 102 16 706 B4 and DE 10 2004 048 500 A1.

It is an object of the invention to decrease the costs for producingheadlight lenses for motor vehicle headlights. It is a further object ofthe invention to produce a particularly high quality headlight lens fora motor vehicle headlight within a restricted cost frame.

The above object is achieved by a method for blank molding or producinga motor vehicle headlight or a lens for a motor vehicle headlight,wherein a blank made of glass is produced, the temperature gradient ofthe blank is inverted, and wherein subsequently the headlight lens for amotor vehicle or the lens for a motor vehicle headlight is pressed fromthe blank.

Appropriate glass types may be, for example, B270, F2, DOCTAN®.

In a further embodiment of the invention the blank is produced frommolten glass, which is molded and/or shaped. In a further embodiment ofthe invention the mass of the blank is in the range of 50 g to 250 g.

In a further embodiment of the invention the temperature gradient of theblank is adjusted such that the temperature of the core of the blank ismarkedly above room temperature. In a further embodiment of theinvention the temperature gradient of the blank is adjusted such thatthe temperature of the core of the blank is at least 100° C. above roomtemperature.

In a further embodiment of the invention the blank for inverting itstemperature gradient is initially cooled down, particularly with supplyof heat, and subsequently heated, wherein it is considered that theblank is heated such that the temperature of the surface of the blankafter the heating process is at least 100° C., particularly 150° C.higher than the transformation temperature T_(G) of the glass. Thetransformation temperature T_(G) of the glass means the temperature atwhich the glass becomes hardened. Particularly the transformationtemperature T_(G) of the glass in the sense of the invention should meanthe temperature at which the glass has a viscosity-log value in a rangearound 13.2 (corresponding to 10^(13.2) Pas), particularly between 13(corresponding to 10¹³ Pas) and 14.5 (corresponding to 10^(14.5) Pas).With respect to glass type B270 the transition temperature T_(G) isabout 530° C.

In a further embodiment of the invention the blank is cooled down at atemperature between 300° C. and 500° C., particularly between 350° C.and 450° C. In a further embodiment of the invention the blank is cooleddown at a temperature between 20K and 200K, particularly between 70K and150K, beneath the transformation temperature T_(G) of the glass of theblank. In a further embodiment of the invention the blank is heated at atemperature between 1000° C. and 1250° C.

In a further embodiment of the invention the temperature gradient of theblank is adjusted such that the temperature of the core of the blank isat least 50K beneath the surface temperature of the blank. In a furtherembodiment of the invention the blank is cooled such that thetemperature of the blank before the heating process is from T_(G)-80K toT_(G)+30K. In a further embodiment of the invention the temperaturegradient of the blank is adjusted such that the core temperature of theblank is 450° C. to 550° C. The temperature gradient is preferablyadjusted such that the temperature within the core of the blank is lowerthan T_(G) or close to T_(G). In a further embodiment of the inventionthe temperature gradient of the blank is adjusted such that the surfacetemperature of the blank is in the range from 700° C. to 900° C.,particularly 750° C. to 850° C. In a further embodiment of the inventionthe blank is heated such that its surface (particularly immediatelybefore the molding process) assumes a temperature corresponding to thetemperature at which the glass of the blank has a viscosity-log valuebetween 5 (corresponding to 10⁵ Pas) and 8 (corresponding to 10⁸ Pas),particularly a viscosity-log value between 5.5 (corresponding to10^(5.5) Pas) and 7 (corresponding to 10⁷ Pas).

In a further embodiment of the invention the blank for inverting itstemperature gradient is moved (particularly substantially continuously)lying on a cooled lance through a tempering device (for cooling an/orheating the blank). An appropriate cooled lance is disclosed in DE 10100 515 A1. In a further preferred embodiment of the invention a coolantflows through the lance according to a reverse flow principle. In afurther preferred embodiment of the invention the coolant isadditionally or actively heated.

The above object may also be achieved by a device for blank molding aheadlight lens for a motor vehicle or a lens for a motor vehicleheadlight, particularly for carrying out a method including one or moreof the above mentioned features, wherein the device includes a meltingaggregate, a blank device for producing a blank disposed downstream ofthe melting aggregate, a tempering device disposed downstream of theblank device via which the temperature gradient of the blank can beinverted, and a press for molding the blank into the headlight lens fora motor vehicle or the lens for a motor vehicle headlight disposeddownstream of the tempering device.

In a further embodiment of the invention the melting aggregate isdesigned as a tub or pan for melting glass. In a further embodiment ofthe invention the device includes a cooling zone for cooling theheadlight lens for a motor vehicle or the lens for a motor vehicleheadlight disposed downstream of the press. In a further embodiment ofthe invention the temperature gradient of the blank is adjustable viathe tempering device such that the core temperature of the blank ismarkedly above room temperature. In a further embodiment of theinvention the temperature gradient of the blank is adjustable via thetempering device such that the core temperature of the blank is at least100° C. above room temperature.

In a further embodiment of the invention the tempering device isprovided with at least one cooled lance for (particularly substantiallycontinuously) conveying the blank through the tempering device or forholding the blank within the tempering device. An appropriate cooledlance is disclosed in DE 101 00 515 A1. In a further embodiment of theinvention a coolant flows through the lance according to a reverse flowprinciple. In a further embodiment of the invention the coolant isadditionally or actively heated.

It is particularly considered that the blank is removed from a mould forforming or producing the blank before inverting the temperaturegradient. It is particularly considered that inverting the temperaturegradient occurs outside a mould.

Cooling with supply of heat in the sense of the invention should meancooling at a temperature of more than 100° C.

A motor vehicle in the sense of the invention particularly means asurface vehicle usable individually in road traffic. Motor vehicles inthe sense of the invention particularly are not limited to surfacevehicles having combustion engines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general arrangement diagram of a device for producingtechnical glass parts meeting high requirements with respect to contouraccuracy and surface quality, particularly precision lenses;

FIG. 2 shows an exemplary flow diagram of a method for producingtechnical glass parts meeting high requirements with respect to contouraccuracy and surface quality, particularly precision lenses;

FIG. 3 shows a perspective view of an example of a blank having acast-on section;

FIG. 4 shows a side view of a blank having a cast-on section accordingto FIG. 3;

FIG. 5 shows a general arrangement diagram of a device for producing aheadlight lens for a motor vehicle or a lens for a motor vehicleheadlight;

FIG. 6 shows an exemplary flow diagram of a method for producing aheadlight lens for a motor vehicle or a lens for a motor vehicleheadlight;

FIG. 7 shows an exemplary blank before entering a tempering device;

FIG. 8 shows an exemplary blank including an inverted temperaturegradient after exiting the tempering device;

FIG. 9 shows a general arrangement diagram of a typical motor vehicleheadlight;

FIG. 10 shows an example of a lens for a motor vehicle headlight; and

FIG. 11 shows another example of a lens for a motor vehicle headlight.

DETAILED DESCRIPTION

FIG. 1 shows—in a general arrangement diagram—a device 1 for carryingout a method for producing technical glass parts meeting highrequirements with respect to contour accuracy and surface quality,particularly precision lenses, shown in FIG. 2. The device 1 forproducing technical glass parts meeting high requirements with respectto contour accuracy and surface quality includes a melting aggregate 2including an (adjustable) outlet 2B, an injection press 3, a transferstation disposed downstream of the injection press 3 designed as a robot4 and tempering devices 5A, 5B, 5C for cooling blanks and injectionmolded parts, respectively and tempering devices 6A, 6B, 6C for heatingblanks and injection molded parts, respectively. A combination oftempering device 5A and tempering device 6A, a combination of temperingdevice 5B and tempering device 6B and a combination of tempering device5C and tempering device 6C, respectively, is a particular example for atempering device in the sense of the claims.

The device 1 for producing technical glass parts meeting highrequirements with respect to contour accuracy and surface quality alsoincludes a transfer station designed as a robot 7 disposed downstream ofthe tempering device 6A, 6B, 6C, a press 8, particularly designed as aprecision press and horizontal press, a transfer station designed as arobot 9 disposed downstream of press 8 and a cooling zone 10. The device1 for producing technical glass parts meeting high requirements withrespect to contour accuracy and surface quality further includes acontrol assembly 15 for its control and adjustment. Control assembly 15provides for a continuous link of the processing steps shown in FIG. 2.

According to the method shown in FIG. 2, glass, in the presentapplication example B270, is melted in melting aggregate 2 in processingstep 20 and discharged metered in processing step 21 followingprocessing step 20 through outlet 2B which may include a plunger. Aprecise shearing device provides for an accurate cut. The glass gobmanufactured in this way is transferred to the injection press disposedbeneath the outlet. The melting aggregate 2 can be operated continuouslyand discontinuously. It is resistant against the glass melts, which areintended for application. As raw materials mixtures, glass residue,refined raw melt or mixtures of these materials come into consideration.

Processing step 21 is followed by a processing step 22 including aninjection molding process via which an injection molded part including ablank (injection molding) and an on-cast section is produced for asubsequent blank molding process. The liquid glass gob thus is placed inan injection press mould and pressed in the mould with high velocity,particularly by applying vacuum. A very variable mould geometry andlarge aspect ratios can be realized. Herein it is important to ensure ahigh surface quality of the injection press mould to produce a highqualitative surface of the blank. Alternatively the glass may also bepressed out of openings of the mould and remain as free surface. Theblank has—apart from the cast-on section—a shape approximatelycorresponding to the eventual shape of the glass part meeting highrequirements with respect to contour accuracy and surface quality, to bepressed, particularly the precision lens to be pressed.

FIG. 3 shows a perspective view of an application example of aninjection molded part 40 and FIG. 4 shows a side view of the injectionmolded part 40. The injection molded part 40 includes a blank 41intended for a subsequent blank molding process, a cylindrical part 42,a cylindrical part 43 and a supporting foot 44. The cylindrical parts 42and 43 together with the supporting foot 44 form a cast-on section.Reference symbol RUE in FIG. 4 refers to a rounded transition. Referencesymbol TUE refers to a tangential transition. The thickness D₄₄ ofsupporting foot 44 referred to by reference symbol D₄₄ is variable anddepends on the amount of glass. The dimensioning in FIG. 4 refers to theunit millimeter. The volume of the blank is preferably between 110% and130% of the volume of the eventually obtained technical glass partmeeting high requirements with respect to contour accuracy and surfacequality, particularly the precision lens.

Processing step 22 is followed by a processing step 23 in which theblank is cooled using one of the tempering devices 5A, 5B, 5C. Fortransfer the transfer station designed as a robot 4 is provided. Theblank may be suspended at its cast-on section or placed in the temperingdevices 5A, 5B and 5C, respectively. The blank is cooled using thetempering devices 5A, 5B, 5C preferably at a temperature between 300° C.and 500° C., particularly between 350° C. and 450° C. In the presentapplication example the injection molded part and thus blank 5 is cooledfor 5 minutes at a temperature of 400° C. For increasing the variabilityat this time blanks can be cycled out and cooled down to roomtemperature separately.

In a subsequent processing step 24 the blank is heated to a temperaturenecessary for molding via one of the tempering devices 6A, 6B, 6C.Herein it is preferably considered that the blank is suspended at itscast-on section or placed in the tempering devices 6A, 6B and 6C,respectively. The blank preferably is heated such that the temperatureat its surface (particularly immediately before the molding process) isbetween 700° C. and 900° C., particularly between 750° C. and 850° C.

The tempering devices 5A, 5B, 5C and 6A, 6B, 6C for example may bereplaced by a tunnel furnace, particularly including chambers. In thiscase particularly the processing steps 23 and 24 may be combined.

Processing steps 23 and 24 are coordinated such that an inversion of thetemperature gradient is obtained. While the blank before processing step23 (under the assumption of a continuous temperature curve) is insidewarmer than outside after processing step 24 (under the assumption of acontinuous temperature curve) it is outside warmer than inside. Thetemperature gradient is preferably adjusted such that the temperaturewithin the core of the blank is beneath or close to T_(G). Herein thecontrol parameters are the temperature in the tempering devices 5A, 5B,5C and 6A, 6B, 6C and the dwell time of the blank inside the temperingdevices 5A, 5B, 5C and 6A, 6B, 6C. It is preferable to rotate theblank—held at its on-cast section—during processing steps 23 and 24.

If blanks are cycled out they are cooled down to room temperatureseparately and subsequently cycled in again and heated discontinuously.

Processing step 24 is followed by processing step 25 in which the blankis placed in press 8 at the cast-on section via the robot 7 and pressed,particularly on both sides, into a technical glass part meeting highrequirements with respect to contour accuracy and surface quality,particularly the precision lens. In a preferred embodiment the press 8is oriented horizontally (horizontal press). Subsequently the technicalglass part meeting high requirements with respect to contour accuracyand surface quality, particularly the precision lens, is removed viarobot 9 in a processing step 26 and supplied to the cooling zone 10.Herein the cooling process is carried out in a conventional manner,wherein the cast-on section is embedded into the bearing and holdingconcept and removed subsequently to the cooling process.

Depending on the requirements to the products the processing steps arecarried out under air-conditioned cleanroom conditions. The blank—apartfrom the molding process—is only touched at the cast-on section so thatthe (eventual) optically effective surfaces are not touched.

In one embodiment between processing step 22 and processing step 25 anadditional processing step may be provided in which a fire polishingprocess for improving the surface quality is carried out. In this casethe device 1 for producing technical glass parts meeting highrequirements with respect to contour accuracy and surface qualityincludes corresponding mechanisms for implementing the fire polishingprocess.

FIG. 5 shows—in a general arrangement diagram—the device 101 forimplementing a method for producing headlight lenses for a motor vehicleshown in FIG. 6 such as headlight lens 202 for a motor vehicle shown inFIG. 9 or lenses for motor vehicle headlights such as lenses 250 and 260for motor vehicle headlights shown in FIG. 10 and FIG. 11. Device 101includes a melting aggregate 102, such as a tub or pan, in which in aprocessing step 120 glass is molted, in the present application exampleB270 or DOCTAN®. Melting aggregate 102 may include, for example, anadjustable outlet. Upstream from melting aggregate 102 liquid gas issupplied in processing step 121 into a blank device 103 for producing ablank, particularly having a mass of 50 g to 250 g, such as a gob or ablank close to final contours (a blank close to final contours has acontour which is similar to the contour of the headlight lens for amotor vehicle or a lens for a motor vehicle headlight to be pressed,i.e., molded). This may include, for example, moulds into which apre-defined amount of glass is poured. Using the blank device 103, theblank is produced in a processing step 122.

Processing step 122 is followed by a processing step 123 in which theblank is transferred using a transfer station 104 to one of the coolingdevices 105A, 105B or 105C and is cooled using the cooling device 105A,105B or 105C at a temperature between 300° C. and 500° C., particularlybetween 350° C. and 450° C. In the present application example the blankis cooled for more than 10 minutes at a temperature of 400° C. such thatits temperature in the inside is about 500° C.

In a subsequent processing step 124 the blank is heated using theheating devices 106A, 106B or 106C at a temperature between 1000° C. and1250° C., wherein preferably it is considered that the blank is heatedsuch that the surface temperature of the blank after the heating processis at least 100° C., particularly at least 150° C., above T_(G), and isparticularly in the range of 750° C. to 850° C.

A combination of cooling device 105A and heating device 106A, acombination of cooling device 105B and heating device 106B and acombination of cooling device 105C and heating device 106C,respectively, in the sense of the claims is an example for a temperingdevice for adjusting the temperature gradient.

Processing steps 123 and 124 are—as explained in the following withrespect to FIG. 7 and FIG. 8—coordinated such that an inversion of thetemperature gradient is achieved. FIG. 7 shows an example of a blank 130before entering one of the cooling devices 105A, 105B or 105C and FIG. 8shows the blank 130 including an inverted temperature gradient afterexiting one of the heating devices 106A, 106B or 106C. While the blankbefore processing step 123 (under the assumption of a continuoustemperature curve) is inside warmer than outside after processing step124 (under the assumption of a continuous temperature curve) it isoutside warmer than inside. The wedges indicated by reference symbols131 and 132 represent the temperature gradients, wherein the width ofone of the wedges 131 and 132, respectively, represents a temperature.

For inverting the temperature gradient in a particular embodiment ablank is moved (particularly substantially continuously) lying on acooled lance (not shown) through a tempering device including one of thecooling devices 105A, 105B or 105C and one of the heating devices 106A,106B or 106C or held in one of the cooling devices 105A, 105B or 105Cand/or one of the heating devices 106A, 106B or 106C. An appropriatecooled lance is disclosed in DE 101 00 515 A1. Preferably a coolantflows through the lance according to a reverse flow principle.Alternatively or additionally it can be contemplated to heat the coolantadditionally or actively.

Downstream of the heating devices 106A, 106B, 106C a press 108 isprovided to which a blank is transferred via a transfer station 107. Theblank is blank molded, particularly on both sides, using press 108 in aprocessing step 125 into a headlight lens for a motor vehicle or a lensfor a motor vehicle headlight. Subsequently the headlight lens for amotor vehicle or the lens for a motor vehicle headlight is transferredto a cooling zone 110 via a transfer station 109. The headlight lens fora motor vehicle or the lens for a motor vehicle headlight is cooled in aprocessing step 126 via the cooling zone 110. The device 10 shown inFIG. 5 further includes a control assembly 115 for controlling oradjusting the device 101 shown in FIG. 5. The control assembly 115preferably provides for a continuous link between the individualprocessing steps.

The elements or components in FIG. 1, FIG. 5, FIG. 7, FIG. 8 and FIG. 9are shown taking into consideration simplicity and clarification and arenot necessarily to scale. For example the dimensions of some elementsare shown exaggerated compared to other elements for improving theunderstanding of the application examples of the present invention.

1-54. (canceled)
 55. A method of blank molding a headlight lens for amotor vehicle headlight, the method comprising: producing a blank fromglass; inverting the temperature gradient of the blank by cooling at atemperature between 20K and 200K beneath the transformation temperatureT_(G) of the glass of the blank and heating the blank; and subsequentlyblank molding the headlight lens from the blank.
 56. The method of claim55, wherein the temperature of the blank before the heating is in therange of T_(G)-80K to T_(G)+30K;
 57. The method of claim 56, wherein theblank is heated such that its surface temperature assumes a temperaturecorresponding to a temperature at which the glass of the blank has aviscosity between 105 Pas and 108 Pas.
 58. The method of claim 57,wherein the mass of the blank is in the range of 50 g to 250 g.
 59. Themethod of claim 55, wherein the blank is heated such that its surfacetemperature assumes a temperature corresponding to a temperature atwhich the glass of the blank has a viscosity between 105 Pas and 108Pas.
 60. The method of claim 59, wherein the temperature gradient of theblank is adjusted such that the temperature in the core of the blank isalways at least 100° C. above room temperature.
 61. The method of claim55, wherein the temperature gradient of the blank is adjusted such thatthe temperature in the core of the blank is always at least 100° C.above room temperature.
 62. The method of claim 55, wherein the blank iscooled at a temperature between 300° C. and 500° C.
 63. A method ofblank molding a headlight lens for a motor vehicle headlight, the methodcomprising: producing a blank from glass; inverting the temperaturegradient of the blank by cooling and subsequently heating the blank,wherein the blank is cooled such that the temperature of the blankbefore the heating is in the range of T_(G)-80K to T_(G)+30K; andsubsequently blank molding the headlight lens from the blank.
 64. Themethod of claim 63, wherein the blank is heated such that its surfacetemperature assumes a temperature corresponding to a temperature atwhich the glass of the blank has a viscosity between 105 Pas and 108Pas.
 65. The method of claim 64, wherein the mass of the blank is in therange of 50 g to 250 g.
 66. The method of claim 65, wherein thetemperature gradient of the blank is adjusted such that the temperaturein the core of the blank is always at least 100° C. above roomtemperature.
 67. The method of claim 63, wherein the temperaturegradient of the blank is adjusted such that the temperature in the coreof the blank is at least 100° C. above room temperature.
 68. The methodof claim 63, wherein the blank is cooled at a temperature between 300°C. and 500° C.
 69. A method of blank molding a headlight lens for amotor vehicle headlight, the method comprising: producing a blank fromglass; inverting the temperature gradient of the blank by cooling andsubsequently heating the blank such that the viscosity at the surface ofthe blank is at least 105 Pas lower than the viscosity of the core ofthe blank; and subsequently blank molding the headlight lens from theblank.
 70. The method of claim 69, wherein the mass of the blank is inthe range of 50 g to 250 g.
 71. The method of claim 69, wherein thetemperature gradient of the blank is adjusted such that the temperaturein the core of the blank is always at least 100° C. above roomtemperature.
 72. The method of claim 69, wherein the blank is cooled ata temperature between 300° C. and 500° C.
 73. A method of producing atechnical glass part meeting high requirements with respect to contouraccuracy and surface quality, the method comprising: producing a blankincluding a cast-on section using an injection molding process; coolingand subsequently heating the blank, wherein the blank is held suspendedat the cast-on section during at least one of (a) the cooling of theblank and (b) the heating of the blank; and subsequently blank moldingthe blank into a technical glass part meeting high requirements withrespect to contour accuracy and surface quality.
 74. The method of claim73, wherein the volume of the cast-on section is larger than the volumeof the blank.
 75. The method of claim 73, wherein the blank is cooleddown at a temperature between 20K and 200K beneath the transformationtemperature of the glass of the blank.
 76. A method of producing aprecision lens, the method comprising: producing a blank including acast-on section using an injection molding process, wherein the cast-onsection includes a supporting foot; cooling and subsequently heating theblank, wherein the blank is mounted upright via the supporting footduring at least one of (a) the cooling of the blank and (b) the heatingof the blank; and subsequently blank molding the blank into a precisionlens.
 77. The method of claim 76, wherein the volume of the cast-onsection is larger than the volume of the blank.
 78. The method of claim76, wherein the blank is cooled at a temperature between 20K and 200Kbeneath the transformation temperature of the glass of the blank.